The sizes that matter
YouTube thumbnail: 1280×720. Instagram post: 1080×1350 (4:5). Stories, Reels and TikTok: 1080×1920 (9:16). X post image: 1600×900. LinkedIn and Facebook link image: 1200×627 and 1200×630. Banners: YouTube 2560×1440, LinkedIn 1584×396, X 1500×500.
Leave room for the interface
On 9:16 Stories, Reels and TikTok, the top and bottom are covered by buttons and captions. Keep faces and text in the middle. On banners, profile pictures cover a corner — and YouTube shows only the middle strip of a banner on phones.